On Thu, Nov 04, 2021 at 04:21:12PM +0100, Alexandre Ratchov wrote: > The current sndiod latency (minimum time between when the program > plays something and when sound reaches Joe's ears) is too large and > makes OpenBSD unpleasant to use for telephony, games, and makes > controls of video players slugish. > > The defaut latency (of 160ms) was set ~10 years ago to workaround > various problems: KERNEL_LOCK used to block audio processing for very > long, azalia(4) and uaudio(4) were unable to recover after an error, > which aggravated the problem. > > The kernel improved a lot the last decade and such large buffers are > not necessary anymore. I think something between 20ms and 40ms is a > better default for the average OpenBSD system: > > * audio-conferencing software and games requires no sndiod_flags > tweaks anymore > > * on modern machines (like my 7 years old i5-2500K) building a kernel > doesn't make audio stutterer > > * sndiod_flags tweaks will still be needed for: > - very slow or overloaded machines used for audio > - machines running heavy/bogus SMM code > - real-time synths & effects (20ms is still too small) > > Please try to switch you system to 40ms buffers (i.e. 1920 samples at > the default 48kHz rate), for instance either apply diff below or > simply do: > > rcctl set sndiod flags -z 480 -b 1920 > rcctl restart sndiod
This introduces noticable stuttering on my X230 runs a few xterms and firefox with idle tabs. The one thing I always use for testing audio is `pkg_add -u' while playing `mpv songXY.ogg': whether or not it installs pacakges does not matter. A noop run is enough to notice stuffer with this diff while the current sndio defaults do not produce any stutter. > then report any significant increase of stuttering, and what > software/hardware triggers it. If you think 20ms or 30ms (i.e. 960 and > 1440 sample buffers) are better, let me know as well. Trying above rcctl lines with `-b 1440' and `-b 960' made it worse: more stutter and noticably slower sound playback, in increasing order. ^Z the pkg_add process restores audio to normal. `fg' it brings stutter back, i.e. without `pkg_add' running I hear no difference using any of the three values. > Note that OpenBSD is not real-time (neither are programs we run) so > audio may stutter no matter how large the buffers are. The goal here > is to get a ballance between disconfort caused by latency and > probability of stuttering for the average OpenBSD system. > > If we reach a consensus, here's the diff to make above settings the > default. > > OK? > > Index: sndiod.c > =================================================================== > RCS file: /cvs/src/usr.bin/sndiod/sndiod.c,v > retrieving revision 1.47 > diff -u -p -r1.47 sndiod.c > --- sndiod.c 1 Nov 2021 14:43:25 -0000 1.47 > +++ sndiod.c 1 Nov 2021 15:28:37 -0000 > @@ -82,7 +82,7 @@ > * buffer size if neither ``-z'' nor ``-b'' is used > */ > #ifndef DEFAULT_BUFSZ > -#define DEFAULT_BUFSZ 7680 > +#define DEFAULT_BUFSZ 1920 > #endif > > void sigint(int); > So at least for my setup this is not an improvement. I quickly tried the mid-value between 7680 and 1920, 4800, and with that I hear no stutter while `pkg_add' is running! Smaller values probably work but I didn't bisect it to the lowest possible value.
